In 1992, after his studies of agricultural sciences at the Swiss Federal Institute of Technology (ETH) in Zurich, Hans Dieter Hess was granted a scholarship for a doctoral thesis at the Centro Internacional de Agricultura Tropical (CIAT) in Colombia.

After defending the thesis in 1995, he acted as scientific adviser at the National Program of Animal Nutrition at Corpoica (Corporación Colombiana de Investigación Agropecuaria) in Colombia. In 1999, he went back to Switzerland, and worked as technical adviser in the private feed industry.

In 2000, Hans Dieter Hess joined again ETH, initially as postdoctoral fellow and subsequently a senior assistant. Beside the coordination of the implementation of project activities in Latin-American and West Asia, his duties include the cooperation with funding agencies, the monitoring and evaluation of projects, the technical and financial reporting, the organization of scientific and technical meetings and workshops, and the elaboration of publications.

In 2005, he joined Agroscope Liebefeld-Posieux (ALP; formerly Swiss Federal Research Station for Animal Production and Dairy Products), and in 2008 he was named head of the section “Safety and Quality” at ALP. This section includes, among others, the official feed inspection and the national reference laboratory for milk and dairy products.